(a) Field of the Invention
The invention relates to an equalization apparatus, particularly to an equalization apparatus capable of equalizing a stub effect.
(b) Description of the Related Art
In general, an equalizer located at the receiver end is to equalize a signal attenuation effect on the channel so that the signal is equalized back to the transmitted signal of the transmitter end. However, accompanying with the increase in the data transmission speed, the transmitted signal at the transmitter end has a stub effect due to the stub problem from the printed circuit board.
FIG. 1A shows a transmission system 100. The transmission system 100 comprises a transmitter end 102, a cable line 104, and a receiver end 106 where the transmitter end 102 comprises a high-definition multimedia interface (HDMI) transmitter 108, a display port interface transmitter 110, and a printed circuit board (PCB) metal line 112.
For a system having multiple application specifications, the PCB metal line 112 of the transmitter end 102 may have a branch point, such as the point A. In the case of having a branch point, the transmitted signal Vcable transmitted from the point C at the transmitter end 102 may have a stub effect. The details should be referred to FIG. 1B.
FIG. 1B shows waveform graphs of the transmission signal Va, the transmission signal Vb, and the transmission signal Vcable. As shown in the waveform graphs, when the signal transmitted by the HDMI transmitter 108 hits the branch point A, the transmitted signal is divided into two, that is, the transmission signal Va and the transmission signal Vb. The transmission signal Va is transmitted from the point A directly to the point C while the transmission signal Vb is transmitted from the point A to the point B, then reflected from the point B to the point A, and again transmitted to the point C. Since the transmission signal Vb has to pass through a stub (that is, AB segment) and then be reflected back to the point C, the transmission signal Vb has delay time Td1 compared to the transmission signal Va. Thus, at the point C, after the transmission signal Va combines with the transmission signal Vb, the transmission signal Vcable has a stub effect, that is, delay time Td1. However, if the transmission signal Vcable outputted by the transmitter end 102 has a stub effect, after the signal is attenuated due to passing the transmission line, the data may not be recovered correctly at the receiver end 106.